icm/failover_timeout is a SAP Parameter attribute which is used to control Timeout to cancel JCo connection information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
If a JCo connection that uses the ICM as a proxy cancels, this
connection can be taken over by another process. This must happen within
the time period, otherwise the connection is deleted from ICM.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.